Method for Determining the Properties of the Content of an Arc Furnace

ABSTRACT

In a method for determining a dividedness and/or position of a batch material ( 7 ) existing essentially in the solid phase in an arc furnace ( 1 ) having a furnace vessel ( 2 ), acoustic signals (N e , N g , N d ) are generated by an arc discharge ( 6 ) between an electrode ( 3   a   , 3   b   , 3   c ) and the batch material ( 7 ). The acoustic signals (N e , N g , N d ) reflected and/or transmitted through by the batch material ( 7 ) are measured by acoustic sensors ( 5   a   , 5   b   , 5   c   , 5   e   , 5   g   , 5   h   , 5   s   , 5   t ), wherein at least one acoustic sensor ( 5   a   , 5   b   , 5   c   , 5   e   , 5   g   , 5   h   , 5   s   , 5   t ) is provided per segment (S n ) of the furnace vessel ( 2 ) subdivided into a plurality of segments (S n ), and wherein the dividedness and/or position of the batch material ( 7 ) in the arc furnace ( 1 ) is determined by evaluating the measured acoustic signals (N e , N g , N d ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage application of InternationalApplication No. PCT/EP2006/063643 filed Jun. 28, 2006, which designatesthe United States of America, and claims priority to German applicationnumber 10 2005 034 378.3 filed Jul. 22, 2005, the contents of which arehereby incorporated by reference in their entirety.

TECHNICAL FIELD

The invention relates to a method for determining the status of thecontent of an arc furnace for melting a batch material.

BACKGROUND

A batch material, for example scrap metal, is melted in an arc furnaceby supplying energy. In an electric arc furnace for producing steel, forexample, energy is supplied to the batch material by forming an arcdischarge with the aid of electrodes. Chemical energy is in this casepreferably also put in using additional combustible materials which, forexample, at least partially comprise coal and/or oxygen.

The process taking place in the arc furnace depends essentially on thestatus of the content of the electric arc furnace. It is known to sortand classify scrap metal, and to supply scrap metal to the electric arcfurnace in a sorted fashion while following a loading plan. Conclusionscan then be made regarding the state inside the furnace based on thescrap metal sorting and based on the loading plan, although these sufferfrom a comparatively high level of uncertainty and susceptibility toerror.

SUMMARY

According to an embodiment, a method for determining a dividednessand/or position of a batch material existing essentially in the solidphase in an arc furnace having a furnace vessel, may comprise the stepsof: generating acoustic signals by an arc discharge between an electrodeand the batch material, and measuring the acoustic signals reflectedand/or transmitted through by the batch material by means of acousticsensors, wherein at least one acoustic sensor is provided per segment ofthe furnace vessel subdivided into a plurality of segments, and whereinthe dividedness and/or position of the batch material in the arc furnaceis determined by evaluating the measured acoustic signals.

According to another embodiment, a device for determining a dividednessand/or position of a batch material existing essentially in the solidphase in an arc furnace having a furnace vessel, may comprise: means forgenerating acoustic signals by an arc discharge between an electrode andthe batch material, and acoustic sensors for measuring the acousticsignals reflected and/or transmitted through by the batch material,wherein at least one acoustic sensor is provided per segment of thefurnace vessel subdivided into a plurality of segments, and wherein thedividedness and/or position of the batch material in the arc furnace isdetermined by evaluating the measured acoustic signals.

According to a further embodiment, at least one acoustic sensor, whichis arranged on the furnace vessel and/or on other parts of the arcfurnace, can be used for measuring the acoustic signals. According to afurther embodiment, electrical signals can be additionally measured withthe aid of at least one electrical sensor in order to determine thedividedness and/or position in the arc furnace. According to a furtherembodiment, electrical signals can be measured between at least twoelectrodes of the arc furnace by means of an electrical sensor.According to a further embodiment, measurement values and data obtainedfrom the measurement values can be stored in a database for earlydetection of a collapse of the batch material. According to a furtherembodiment, measurement values and data obtained from the measurementvalues can be compared with measurement values and with data which arestored in the database. According to a further embodiment, the methodmay further comprise the step of: using the determined dividednessand/or position of the batch material of the arc furnace for controllingor regulating the arc furnace. According to a further embodiment, inorder to avoid breakage of one or more of the electrodes, the energysupply to the electrodes can be regulated. According to a furtherembodiment, the position of the electrodes can be regulated. Accordingto a further embodiment, the arc furnace may be deliberately operatedasymmetrically. According to a further embodiment, the supply ofchemical energy into the arc furnace can be regulated.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and details of the invention will be described belowwith the aid of examples in conjunction with the drawings, in which:

FIG. 1 schematically shows an arc furnace coupled to a computing deviceand having a furnace vessel,

FIG. 2 shows the furnace vessel in a schematic representation

FIG. 3 shows a segment of the furnace vessel,

FIG. 4 schematically shows an example of the propagation of acousticsignals in the furnace vessel.

DETAILED DESCRIPTION

According to an embodiment, in a method for determining the status ofthe content of an arc furnace, in particular an electric arc furnace,acoustic signals from the arc furnace are measured. In this way, andparticularly by evaluating the measured acoustic signals, the status ofthe content of the arc furnace, in particular of the electric arcfurnace, can be determined substantially more accurately and reliably.By the improved method according to an embodiment for determining thestatus of the content of an arc furnace, the energy input into the arcfurnace, in particular an electric arc furnace, can be better regulatedlocally and quantitatively.

At least one acoustic sensor which may be arranged on the furnace vesseland/or on other parts of the arc furnace, in particular the electric arcfurnace, can be advantageously used for measuring the acoustic signals.

Advantageously electrical signals, in particular current, voltage and/orenergy, can be additionally measured with the aid of at least oneelectrical sensor in order to determine the status of the content of thearc furnace, in particular the electric arc furnace. Substantially moreaccurate information regarding the status of the content of the arcfurnace can be obtained in this way, in particular by combinedevaluation of the measurement data obtained both from acousticmeasurement and from electrical measurement.

Electrical signals, in particular current, voltage and/or energy, can beadvantageously measured between at least two electrodes of the arcfurnace by means of an electrical sensor.

The status of the batch material, which advantageously consists at leastpartially of scrap metal, may be advantageously determined.

Measurement values and/or data obtained from the measurement values maybe advantageously stored in a database for early detection of collapsesof the batch material.

Instantaneous measurement values and/or data obtained from themeasurement values may be advantageously compared with measurementvalues and/or with corresponding data which are stored in the database.

A status of the content of the arc furnace, which with a high likelihoodwill lead to a collapse of the batch material and/or to damage at theelectrodes, can thereby be detected particularly promptly. It istherefore possible to counteract such events in time.

In the method for operating an arc furnace, wherein information aboutthe status of the content of the arc furnace, which has been determinedwith the aid of a method as described above, the information can be usedfor controlling or regulating the arc furnace.

The energy supply to the electrodes may be advantageously regulated inorder to avoid breakage of one or more of the electrodes.

The position of the electrodes can be advantageously regulated.

Advantageously, the arc furnace can be deliberately operatedasymmetrically, i.e. the position of the electrodes and/or the energysupply to the electrodes is at least temporarily set non-symmetrically.

The supply of chemical energy into the arc furnace can be advantageouslyregulated.

According to another embodiment, a device may have means suitable forcarrying out a method as described above, the device comprising an arcfurnace with acoustic sensors.

FIG. 1 shows an arc furnace 1, which is designed as an electric arcfurnace in the exemplary embodiment. The arc furnace 1 comprises aplurality of electrodes, three electrodes 3 a, 3 b, 3 c in the exampleshown, which preferably are arranged so that their position can bemodified and which extend at least partially into the furnace vessel 2of the electric arc furnace.

Electrical current can preferably flow between the electrodes 3 a, 3 b,3 c and/or between the electrodes 3 a, 3 b, 3 c and the furnacecontainer 2. Owing to this, an electric arc discharge 6 is formed in thefurnace vessel 2. The arc discharge 6 is indicated merely symbolicallyin the drawing. In order to measure electrical signals ES, for examplein order to measure the current between the electrodes 3 a, 3 b, 3 c, anelectrical sensor 4 a is provided. Acoustic sensors 5 a, 5 b, 5 c, 5 e,5 g, 5 h, 5 s, 5 t, with the aid of which acoustic signals N_(d), N_(e),N_(g) (see FIG. 4) from inside the arc furnace 1 can be recorded, arearranged around the arc furnace 1. Measurement data of the acousticsensors 5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t are delivered to suitableevaluation means 11. Optionally, measurement data of the at least oneelectrical sensor 4 a are also delivered to the suitable evaluationmeans 11.

The acoustic sensors 5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t are arrangedaround the furnace vessel 2 in the example shown. Acoustic sensors 5 a,5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t may be arranged not only on thefurnace vessel 2 but also, as an alternative or in addition, for exampleon a cover (not represented in detail) of the arc furnace 1. Acousticsensors 5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t may, for example, bearranged so that they are connected indirectly and/or directly to thefurnace vessel 2 and/or to the arc furnace 1.

It is, however, particularly advantageous to arrange the acoustic sensor5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t directly on the furnace container2 and/or on the cover (not represented in detail) of the arc furnace 1.

A computing device 10 is advantageously provided, to which the arcfurnace 1 is coupled. The computing device 10 sends control signals CSto the arc furnace, for example in order to influence the position ofthe electrodes 3 a, 3 b, 3 c and/or the energy supply to the electrodes3 a, 3 b, 3 c. To this end, the computing device 10 comprises a controlmodule 12. The computing device 10 preferably comprises evaluation means11 with the aid of which measurement data, which are communicated fromthe plurality of acoustic sensors 5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 tand/or the at least one electrical sensor 4 a, are optionally processedand analyzed. A structure-borne noise analysis is carried out byevaluating the signals of the acoustic sensors 5 a, 5 b, 5 c, 5 e, 5 g,5 h, 5 s, 5 t.

As schematically represented in FIG. 2, the furnace vessel 2 may besubdivided into one or more segments S_(n) with an angle α_(n). Thesegments S_(n) preferably have a uniform angle α_(n). In an alternativeconfiguration, the angle α_(n) may differ from segment S_(m) to segmentS_(n). It is, for example, possible to divide the furnace vessel 2 intosegments S_(n) so that the segments S_(n) are arranged at leastapproximately with point symmetry. Preferably, at least one acousticsensor 5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t is provided per segmentS_(n). In an exemplary configuration according to an embodiment, it ispossible for no acoustic sensor 5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 tto be provided in one or more segments S_(n). According to anembodiment, however, at least one acoustic sensor 5 a, 5 b, 5 c, 5 e, 5g, 5 h, 5 s, 5 t is provided. Preferably, at least two acoustic sensors5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t are provided.

As schematically indicated in FIG. 3, a segment S_(n) with an angleα_(n) may be further decomposed into a horizontal segments h_(s1),h_(s2), . . . , h_(sn) and/or vertical segments v_(s1), v_(s2), . . .v_(sn), in order to establish the arrangement of the acoustic sensors 5a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t.

FIG. 4 schematically shows a detail of an arc furnace 1, and inparticular the content of the furnace vessel 2 and the electrode 3 a arerepresented merely schematically. The furnace vessel 2 contains thebatch material 7, in particular scrap metal, which is melted with theaid of at least one electrode 3 a to form a melt 8, in particular liquidsteel. The batch material 7 is melted in particular by supplying energyto the interior of the arc furnace 1 by the action of the arc discharge6 (represented merely schematically), which is formed in particularbetween the electrode 3 a and the batch material 7 or the melt 8. Slag 9may be formed above the melt 8 inside the arc furnace 1.

The batch material 7 is formed by a plurality of pieces, and preferablyexists essentially in the solid phase. The status of the content of thearc furnace 1, in particular the status of the batch material 7, ischaracterized above all by the dividedness of the batch material 7. Thedividedness of the batch material 1 is characterized for example bylength, width, height, position, shape, weight and/or density of thebatch material 7, or of the pieces forming the batch material 7. Thedividedness and in particular the position of the batch material 7, inparticular scrap metal, influences the input of energy into the arcfurnace 1. Said features, or the characteristics of the batch material7, i.e. the status of the content of the arc furnace 1, may cause scrapmetal collapses which can lead to electrode breakages and therefore toshutdown of the arc furnace 1. The input of energy into the arc furnace1 varies owing to inhomogeneity and/or inconsistency of the batchmaterial 7, for which reason the performance capacity of one or morefurnace transformers (not represented in detail in the drawings), whichare coupled to the electrodes 3 a, 3 b, 3 c, cannot fully be utilized.According to an embodiment, it is possible to substantially avoidcollapses of the batch material 7, electrode breakages and furnaceshutdowns.

By suitable regulation, the performance capacity of one or more furnacetransformers can be utilized better. To this end a plurality of acousticsensors 5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t, only a few of which arerepresented by way of example in FIGS. 1 and 4, are preferably arrangedon the furnace vessel 2, in particular on the wall of the furnace vessel2. For structure-borne noise measurement, the acoustic sensors 5 a, 5 b,5 c, 5 e, 5 g, 5 h, 5 s, 5 t are arranged at suitable measurementpositions around the furnace, and optionally also on the furnace cover.With the aid of the acoustic sensors 5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s,5 t, a structure-borne noise analysis can be carried out. At the sametime available current signals, i.e. electrical signals ES (see FIG. 1),are processed and analyzed by suitable measurement methods. With the aidof the evaluation means 11 represented in FIG. 1, the signals availablefrom both measurement methods (electrical and acoustic measurement) arepreferably processed with the aid of one or more algorithms in the formof a hybrid system to obtain evaluation data.

The acoustic signals N_(d), N_(e), N_(g) are generated in particular bythe arc discharge 6 between the electrode and the batch material 7 ormelt 8. Some of the acoustic signals N_(g), N_(e) are deflected by thebatch material 7, in particular scrap metal. This gives rise toreflected acoustic signals N_(d). Acoustic signals are transmittedthrough the batch material 7 and/or reflected by it. Both may possiblytake place repeatedly and in a different way for various acousticsignals N_(d), N_(e), N_(g). The acoustic signals are transmittedfurther at the wall (sidewalls, panels and also cover) of the furnacecontainer 2, in particular through the solid body of the batch material7.

By correlating the measurement data determined with the aid of theacoustic sensors 5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t, it is possibleto obtain information about the density of the batch material 7, and inparticular it is possible to determine for example the positions atwhich the highest or lowest scrap metal density exists. By evaluatingthe measurement data obtained with the aid of the acoustic sensors 5 a,5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t, information can be obtained regardingthe dividedness and/or position of the batch material 7 in the arcfurnace 1. Optionally, the electrical signals ES are also taken intoaccount for the evaluation. Owing to this, the arc furnace maydeliberately be operated asymmetrically, in particular based on thedetermination of a scrap metal density, i.e. energy may be deliveredasymmetrically to the electrodes 3 a, 3 b, 3 c and/or the position ofthe electrodes 3 a, 3 b, 3 c may be modified asymmetrically. Theelectrodes 3 a, 3 b, 3 c are preferably arranged so that they can bedisplaced vertically.

The scrap metal density is particularly relevant information inparticular because lower-density scrap metal melts more rapidly thanhigher-density scrap metal. In zones with a lower scrap metal density,the input of energy may be reduced, for example inter alia owing to theabsence of foam slag. On the other hand, the energy input may beincreased by a corresponding amount in zones with a higher scrap metaldensity.

Based on the evaluation of the measurement data obtained with the aid ofthe acoustic sensors 5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t, theelectrical signals ES optionally also being taken into account for theevaluation, the supply of chemical energy into the arc furnace 1 may beregulated. The supply of chemical energy influences or causes acombustion process inside the arc furnace 1. The chemical energy may forexample be supplied into the arc furnace 1 by manipulating a lance (notrepresented in detail in the figures) and/or with the aid of so-calledcoherent jets.

The measurement data obtained from the acoustic measurements areprocessed with the aid of evaluation means 11 to form evaluation data.Evaluation data may for example be employed, as described above, inorder to optimize the input of energy into the arc furnace 1. With theaid of the evaluation data, likely scrap metal collapses may also bepredicted in advance. Evaluation data are preferably also determinedwith the aid of electrical measurements. Measurement data and/orevaluation data may be stored in a database (not represented in detail),and may advantageously be used for predictive regulation of the arcfurnace 1. Data characteristic of the status of the content of the arcfurnace, referred to below as characteristics, are preferably stored inthe database. Signal sequences leading up to a scrap metal collapse may,for example, be stored as a collapse characteristic. With the aid of thedatabase and the characteristics stored therein, a preferablyself-learning system is formed with the aid of which the energy supplyto the electric arc furnace, in particular to the electrodes 3 a, 3 b, 3c, can be regulated so that future scrap metal collapses or electrodebreakages can be avoided.

For the structure-borne noise analysis, or the arrangement of theacoustic sensors 5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t, the furnacevessel 2 is decomposed into segments S_(n) as indicated in FIGS. 2 and3, preferably by being idealized as a cylindrical vessel. The number ofsegments S_(n) and horizontal or vertical segments h_(s1), h_(s2), . . ., h_(sn) and v_(s1), v_(s2), . . . , v_(sn) respectively, is determinedby the representation of the accuracy, or by the accuracy required for acertain reliability value for the operation of the arc furnace 1, or fora certain quality of the melt 8.

Essential concepts according to various embodiments may be summarized inthe following way:

According to an embodiment, in a method for determining the status ofthe content of an arc furnace 1 for melting a batch material 7, inparticular for melting scrap metal, wherein acoustic signals N_(e),N_(g), N_(d) which are measured by at least one, preferably a pluralityof acoustic sensors 5 a, 5 b, 5 c, 5 e, 5 g, 5 h, 5 s, 5 t, areevaluated preferably in conjunction with electrical signals which aremeasured with the aid of at least one electrical sensor 4 a,particularly in order to avoid electrode breakages. According to anembodiment, the productivity of the arc furnace 1 is increased byachieving a higher specific melting power via corresponding regulationof the arc furnace 1, and shutdown times are reduced. The specific meltenergy is reduced by redistributing energy in the arc furnace 1.Furthermore, the wall wear in the arc furnace 1 is decreased by reducingthe radiation energy on the inner walls of the furnace vessel 2 of thearc furnace 1. The electrode consumption can also be reduced accordingto an embodiment.

1. A method for determining a dividedness and/or position of a batchmaterial existing essentially in the solid phase in an arc furnacehaving a furnace vessel, the method comprising the steps of: generatoracoustic signals by an arc discharge between an electrode and the batchmaterials, measuring the acoustic signals reflected and/or transmittedthrough by the batch material by means of acoustic sensor, wherein atleast one acoustic sensor is provided per segment of the furnace vesselsubdivided into a plurality of segments, and wherein the dividednessand/or position of the batch material in the arc furnace is determinedby evaluating the measured acoustic signals.
 2. The method according toclaim 1, wherein at least one acoustic sensor, which is arranged on thefurnace vessel and on other parts of the arc furnace, is used formeasuring the acoustic signals.
 3. The method according to claim 1,wherein electrical signals are additionally measured with the aid of atleast one electrical sensor in order to determine the dividedness and/orposition in the arc furnace.
 4. The method according to claim 3, whereinelectrical signals are measured between at least two electrodes of thearc furnace by means of an electrical sensor.
 5. The method according toclaim 1, wherein at least one acoustic sensor, which is arranged on thefurnace vessel or the other parts of the arc furnace, is used formeasuring the acoustic signals.
 6. The method according to claim 1,wherein measurement values and data obtained from the measurement valuesare stored in a database for early detection of a collapse of the batchmaterial.
 7. The method according to claim 6, wherein measurement valuesand data obtained from the measurement values are compared withmeasurement values and with data which are stored in the database.
 8. Amethod according to claim 1, further comprising the step of: using thedetermined dividedness and/or position of the batch material of arcfurnace for controlling or regulating the arc furnace.
 9. The methodaccording to claim 8, wherein, wherein, in order to avoid breakage ofone or more of the electrodes, the energy supply to the electrodes isregulated.
 10. The method according to claim 8, wherein the position ofthe electrodes is regulated.
 11. The method according to claim 8,wherein the arc furnace is deliberately operated asymmetrically.
 12. Themethod according to claim 8 wherein the supply of chemical energy intothe arc furnace is regulated.
 13. A device for determining a dividednessand/or position of a batch material existing essentially in the solidphase in an arc furnace having a furnace vessel, comprising: means forgenerating acoustic signals by an arc discharge between an electrode andthe batch material, acoustic sensors for measuring the acoustic signalsreflected and/or transmitted through by the batch material, wherein atleast one acoustic sensor is provided per segment of the furnace vesselsubdivided into a plurality of segments, and wherein the dividednessand/or position of the batch material in the arc furnace is determinedby evaluating the measured acoustic signals.
 14. The device according toclaim 13, wherein at least one acoustic sensor, which is arranged on thefurnace vessel and on other parts of the arc furnace, is used formeasuring the acoustic signals.
 15. The device according to claim 13,wherein electrical signals are additionally measured with the aid of atleast one electrical sensor in order to determine the dividedness and/orposition in the arc furnace.
 16. The device according to claim 15,wherein electrical signals are measured between at least two electrodesof the arc furnace by means of an electrical sensor.
 17. The deviceaccording to claim 13, wherein at least one acoustic sensor, which isarranged on the furnace vessel or on other parts of the arc furnace, isused for measuring the acoustic signals.
 18. The method according toclaim 1, wherein measurement values and data obtained from themeasurement values are stored in a database for early detection of acollapse of the batch material.
 19. The method according to claim 1,wherein measurement values or data obtained from the measurement valuesare stored in a database for early detection of a collapse of the batchmaterial.
 20. The method according to claim 19, wherein measurementvalues or data obtained from the measurement values are compared withmeasurement values or with data which are stored in the database.